Conventionally, microfabrication has been carried out by lithography using a photoresist composition in the production of semiconductor devices. The microfabrication is a method for processing inducing the steps of forming a thin film of a photoresist composition on a substrate to be processed such as a silicon wafer, irradiating the thin film with active light such as ultraviolet rays through a mask pattern in which a pattern of a semiconductor device is depicted, developing the pattern, and etching the substrate to be processed such as a silicon wafer by using the obtained photoresist pattern as a protection film. In recent years, however, semiconductor devices have been further integrated, and the active light to be used has had a shorter wavelength from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). This raises serious problems of the effects of diffused reflection from the substrate and standing wave of active light. Consequently, a method for providing a resist underlayer film called bottom anti-reflective coating (BARC) between a photoresist and a substrate to be processed has been widely applied. In order to achieve further microfabrication, a lithography technique using extreme ultraviolet rays (EUV, wavelength 13.5 nm) and electron beams (EB) as the active light has been developed. In the EUV lithography or the EB lithography, a specific anti-reflective coating is not required because the diffused reflection from the substrate and the standing wave are not usually generated. The resist underlayer film, however, has begun to be widely studied as an auxiliary film for improving the resolution of a resist pattern and adhesion.
The resist underlayer film formed between the photoresist and the substrate to be processed described above is generally formed as a thermally curable crosslinking film that does not generate mixing with the resist by carrying out a baking process after the application of a resist underlayer film-forming composition onto the substrate to be processed in order to reduce mixing with the resist stacked as an upper layer. Usually, a crosslinkable compound (a crosslinking agent) and a catalyst (a crosslinking catalyst) for promoting the crosslinking reaction are added to the resist underlayer film-forming composition in addition to the polymer resin as a main component in order to form such a thermally curable film. Particularly, a thermal acid generator such as a sulfonic acid compound, a carboxylic acid compound, and a sulfonic acid ester are mainly used as the crosslinking catalyst.
In recent years, generation of sublimation component (sublimate) derived from the polymer resin and low molecular weight compounds such as the crosslinking agent and the crosslinking catalyst at the time of baking when the resist underlayer film is formed by using the resist underlayer film-forming composition in the lithography process of semiconductor device production has been a new problem. Such a sublimate contaminates the inside of film formation apparatus by attaching and accumulating in the film formation apparatus during the semiconductor device production process. These contaminations may be a defect generation factor by attaching on a wafer as foreign substance. Consequently, a new underlayer film-forming composition is required to be developed such that the sublimate generated from the resist underlayer film is reduced as much as possible. And resist underlayer films showing low sublimate generation property have been studied (refer to, for example, Patent Document 1 and Patent Document 2).